Inert ingredients are typically solvents, preservatives, surfactants, and other substances that are added to herbicides and pesticides, and in many cases, the manufacturers do not have to disclose them in the ingredients list so that they can protect the formulation of the products as trade secrets. There are roughly 4,000 inert ingredients that are currently approved for use by the U.S. Environmental Protection Agency (EPA).

The study found that one ingredient in Roundup, polyethoxylated tallowamine (POEA), is actually more toxic to human embryonic, placental, and umbilical cells than glyphosate by itself. Additionally, their findings show that the combination of the two chemicals could present even higher toxicity to human cells, and the proprietary mixtures could cause cell death even at residual levels, meaning that people who consume crops that were treated with Roundup could face toxic exposure.

Other research teams have set out to study the effects of these inert ingredients and their synergistic effects when combined with other potentially harmful chemicals. The original research team's conclusions suggest that rather than testing the effects of individual ingredients found in these products, the toxicity levels should be established by testing their commercial formulations to gain an accurate understanding of the dangers that they potentially pose.